The present invention relates in general to coal mining devices and in particular to a new and useful planer control device intended for controlling the elevation of a coal planer or plow which is guided at a coal face on a longwall conveyor with the interposition of a planer guide. The device comprises a lifting mechanism mounted on the waste side of the conveyor with the interposition of a bracket. Coal planer controls serve the purpose of compensating for local irregularities of the footwall or floor, or for a deviation of the planer from the desired cutting horizon. To this end, the longwall conveyor is lifted or lowered by means of a lifting mechanism provided at the waste side. In the lowered position, the planer is brought to climbing, in the lifted position to dipping. With the coal planer adjusted to the desired cutting horizon, the lifting mechanism is in its neutral position.
In prior art planer control devices, rocker-type and jib-type controls are primarily used. Both these controls have the disadvantage that, at least with the conveyor in a dipping position, the conveyor trough is lifted from the floor and fine coal from the coal face can migrate to the waste side. This creates fire hazards at the waste side. In addition, with thin seams and high rates of advance, considerable amounts of coal are lost. Further, the lifting mechanism which, in both instances, are hyrdaulically operated cylinders, are continuously under working load. The result is not only increased stresses and shortened life but also drops in the working load, at least partly. In consequence, the conveyor may subside from its adjusted control position spontaneously. This entails an insufficient control of the planer, even in instances where the conveyor is in its normal or climbing position, since in this case again, the control cylinder is usually under working load.
The purpose of the invention is to eliminate these drawbacks.